This is a timelapse of some really cool flowers at my parents' house; they bloom when the sun goes down. I also should have used a faster timing interval here since the flowers actually bloom fairly quickly once they get started. 

I wanted to try this type of timelapse video since I first built my Arduino Intervalometer. Luckily the weather was clear enough that I had a good opportunity for night photography. I set my camera to take 30 second exposures at F8 and set the intervalometer to trigger it once a minute for 2 hours.

Using the Picasa movie creator mode, I set the transition to timelapse and the frame length to 1/24 of a second. This resulted in a nice smooth video of the northern sky rotating around the north star. Note: the video looks much better in full screen HD.

In order to turn the photos into video I used Picasa, which has a great movie creation feature. The movie creator has a timelapse mode that allows you to set how fast you want the frames to last. I went with 1/8 of a second per frame since it makes the video fairly smooth while not blowing through the frames too fast. If I wanted to I could have reduced my timing interval by a third and made a video at the normal 24 frames per second for smoother video.

All you need to create this effect is a lens with a wide enough aperature to create fairly shallow depth of field (the wider the better). I used my Canon 50mm F1.4 lens. For the sleeve I used some cardstock I had laying around, some tape, and a razor blade to cut out the tree shape. 

The photos below show the difference between a picture taken with the cardboard sleeve on and off. I used a Christmas tree in the background to create the small points of light necessary for this effect. Due to the relatively low light necessary for this type of photography a tripod may also be necessary, although these photos were taken hand-held.

The steps are as follows:

• Open the base image as the Background for the composite image
• Dark Layer
  • Open the dark stock image
  • Copy & paste it into a new layer in the composite image
  • Rename the layer Dark
  • Desaturate the original dark stock image
  • Adjust the levels of the dark stock image
  • Create a layer mask for the Dark layer
  • Copy the desaturated dark stock image
  • Paste it into the Dark layer's mask and anchor
• Light Layer
  • Open the light stock image   
  • Copy & paste it into a new layer in the composite image
  • Rename the layer Light
  • Desaturate the original light stock image
  • Invert the colors of the desaturated light stock image
  • Adjust the levels of the light stock image
  • Create a layer mask for the Light layer
  • Copy the desaturated & inverted light stock image
  • Paste it into the Light layer's mask and anchor
• Save the finished composite image

Below from left to right are the base image, the darker and lighter photo used and the HDR photo I made using this method:

This is a fun technique to play around with. Some photos, if taken properly in the right conditions, can gain a whole new dimension when they get a little HDR boost.  

One mistake I made, as you no doubt noticed in my time-lapse video above, was setting the camera to shutter priority mode. This resulted in considerable depth-of-field shift as the camera changed the aperture when the light dimmed from day into night, placing much of the scene out of focus.